使用scanf()读取c中未知数量的整数

Question

I need to read an unknown number of rows, each containing an unknown number of integers, this number varying from row to row.

The integers are separated from each other by a single space and there is no space at the end of the line.

The output being the sum of all integers.

exemple input:

5
2 2
4 4 4
6 6
3 3

output: 39

Answer 1

The fact that the numbers are entered over several lines is actually irrelevant. Basically you just want to sum up numbers entered by the user until the input stream ends.

You probably want something like this:

#include <stdio.h>

int main() {    
  int sum = 0;
  int number;

  while (scanf("%d", &number) == 1)
  {
    sum += number;
  }

  printf("Sum of all numbers is %d\n", sum);
}

End the input with Ctrl + D .

Example of execution:

1 2 3
4 5
6 7
8
Sum of all numbers is 36

Press Ctrl + D after entering 8 .

Explanation of while (scanf("%d", &number) == 1)

scanf returns the number of items successfully scanned or EOF when the input stream ends. So here we decide to stop the loop if scanf returns anything else than 1 (meaning that the user has either pressed Ctrl + D triggering an EOF, or has entered something that is not a number (eg ABC ).